import 'package1' //解析到的是 es6module.js
import 'package1/whatever'; //sub-a.js

// import 'package1/sub'; //Error [ERR_PACKAGE_PATH_NOT_EXPORTED]: Package subpath './sub' is not defined by "exports" in F:\js_workplace\tutorial\node_tutorial\99node中对ES Module的支持\04.package的exports字段\01\node_modules\package1\package.json imported from F:\js_workplace\tutorial\node_tutorial\99node中对ES Module的支持\04.package的exports字段\01\index.mjs
